Question

这是我写的代码。我正在使用Visual Studio并学习如何使用标准模板库。当我尝试从源打印时，ostream_iterator不起作用。它给出了一个巨大的错误列表，那些我无法理解的错误。

这是我尝试在Visual Studio中运行的完整代码。可以在软件设置中出现问题吗？

#include <iostream>
#include <vector>
#include <list>
#include <iterator>
#include <functional>

using namespace std;
//stream_iterator
int main() {
    vector<string> source = { "31", "3113" };
    copy(istream_iterator<string>(cin), istream_iterator<string>(),back_inserter(source));  //can't understand why this won't work
    return 0;
}





These below are the error messages.
    1>------ Build started: Project: StreamIters, Configuration: Debug Win32 ------
    1>  Source.cpp
    1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\iterator(256): error C2679: binary '>>' : no operator found which takes a right-hand operand of type 'std::string' (or there is no acceptable conversion)
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(485): could be 'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_streambuf<char,std::char_traits<char>> *)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(466): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(void *&)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(448): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(long double &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(430): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(double &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(411): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(float &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(392): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned __int64 &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(373): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(__int64 &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(353): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned long &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(335): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(long &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(317): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned int &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(291): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(int &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(272): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned short &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(237): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(short &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(218): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::_Bool &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(211): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::ios_base &(__cdecl *)(std::ios_base &))'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(204): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_ios<char,std::char_traits<char>> &(__cdecl *)(std::basic_ios<char,std::char_traits<char>> &))'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(198): or       'std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_istream<char,std::char_traits<char>> &(__cdecl *)(std::basic_istream<char,std::char_traits<char>> &))'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(1103): or       'std::basic_istream<char,std::char_traits<char>> &std::operator >><char,std::char_traits<char>,_Ty>(std::basic_istream<char,std::char_traits<char>> &&,_Ty &)'
    1>          with
    1>          [
    1>              _Ty=std::string
    1>          ]
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(1093): or       'std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,unsigned char &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(1086): or       'std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,unsigned char *)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(1079): or       'std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,signed char &)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\istream(1072): or       'std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,signed char *)'
    1>          while trying to match the argument list '(std::basic_istream<char,std::char_traits<char>>, std::string)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\iterator(255) : while compiling class template member function 'void std::istream_iterator<std::string,char,std::char_traits<char>,ptrdiff_t>::_Getval(void)'
    1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\iterator(222) : see reference to function template instantiation 'void std::istream_iterator<std::string,char,std::char_traits<char>,ptrdiff_t>::_Getval(void)' being compiled
    1>          c:\users\mahe\documents\visual studio 2013\projects\streamiters\streamiters\source.cpp(19) : see reference to class template instantiation 'std::istream_iterator<std::string,char,std::char_traits<char>,ptrdiff_t>' being compiled
    ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

代码中没有包含标题<string>。虽然所使用的接口确实要求至少提供std::string声明，但不要求您包含的标头提供std::string的定义和/或对其进行操作的函数。我没有安装MSVC ++，但是你所包含的标题似乎提供了std::string的定义，但没有声明输入或输出运算符。

根据经验，你不应该依赖间接包容。相反，您应该始终明确地包含所有相关标头：尽管声明当前可用，但标头可能会更改为不包含其他标头。

为什么我的istream_iterator不起作用？

1 个答案: